Turbulent Boundary Layer Control by Plasma Synthetic Jet Actuator aiming Engineering Application

制作了几种等离子体合成射流执行器(PSJA)，并对其进行了测试，以考察其几何形状对流动诱导特性的影响。研究发现，存在最佳的阳极和阴极宽度比，以最大限度地提高激励器的流速。在低速低涡度风洞中，利用直接剪切力传感器和热线风速仪测量了PSJA对平面湍流边界层的影响。结果表明，PSJA降低了执行器下游的剪应力。这一剪应力降低现象在本研究中首次被直接测量，对工程应用具有重要意义。然而，剪切应力的降低只在执行器附近观察到。通过计算流体力学(CFD)研究了PSJA诱导的流场。考虑介质体力的可压缩流分析清楚地显示了PSJA…越多，就会产生喷流。为了提高NACA012翼型流动分离控制的有效性，进行了闭合回路反馈控制试验。采用热线作为下游传感器的延迟反馈控制(DFC)方法对控制参数具有较强的鲁棒性。我们发现，与开环控制相比，DFC可以将激活PSJA所需的功耗降低一半。通过图像温度图测量来了解PSJA是如何随着流动而产生热量的。本研究利用高压变压器和音频功率放大器产生辉光放电。由于阳极电压和电流之间存在较大的相移，PSJA的效率并不理想，只有一小部分电能转化为流体流动。PSJA下游的温度通常升高30摄氏度。在小通道中，相对湿度效应也用质量流量计进行了研究。通道的高度被设置为比PSJA高度高几倍。总而言之，PSJA引起的质量流量随着相对湿度的增加而减小。我们计划开发使用PSJA的微型泵和旋流器。较少

Several Plasma Synthetic Jet Actuators (PSJA) were made and tested to examine flow induction characteristics affected by their geometry. We found that optimal width ratio of Anode and Cathode exists in order to maximize the flow velocity induced by the actuator. Effects of PSJA on plane turbulent boundary layer were measured by Direct Shear Stress Sensor and Hot-wire Anemonetry in low speed and low turburence wind tunnel. As results, we proved that PSJA reduces shear stress at the downstream of the actuator. This shear stress reduction phenomenon is measured directly at the first time in this study, and is significant for engineering applications. However, the shear stress reduction effects observed only in the vicinity of the actuator. Shear stress was increased as goes downstream from the actuator.Computational Fluid Dynamics (CFD) studies conducted to investigate the flow fields induced by the PSJA. Compressible flow analysis considering dielectric body force clearly showed how PSJA … More induces jet flow. And we also found that vacuum dielectric coefficient can be used to simulate induced flow in sufficient quantitative accuracy.Closed loop feedback control was tested in order to improve the effectivity of the flow separation control on NACA012 airfoil. Delayed feedback control (DFC) method, using hotwire as a downstream sensor, was chosen because of its robustness to the control parameters. We found that DFC can reduce the power consumption needed to activate PSJA in half as compared to open loop control.Image Thermograph measurements were conducted to know how PSJA induces heat along with flow. In this study, glow discharge was generated using high voltage transformer and audio power amplifier. Because of significant phase shift between anode voltage and current, efficiency of the PSJA was not in satisfactory condition, in the sense that small portion of supplied electrical power as transformed into fluid flow. Temperature at downstream of PSJA often raised by 30 degree Celsius.Relative humidity effects also investigated in small channel using mass flow meter. The height of the channel was set to several times higher than the PSJA height. In conclusion, mass flow induced by PSJA tends to be decreased as relative humidity increases.We are planning to develop micro pumps and swirlers using PSJA. Less